Maintenance planning plays an important role in assets management especially when it directly affects asset availability. In the aviation industry, maintenance planning becomes even more important due to safety aspects, the high availability expectations from aircraft operators and the high costs incurred when an aircraft needs to be taken out of service for repair. Gathering and combining all of the relevant information to generate an optimized maintenance planning is not a simple task.
Repairable items are, generally speaking, components or assets that, after a failure, are submitted to a repair cycle to be used again instead of being discarded. This implies that a repairable item spare part inventory system uses a repair shop where failed components are repaired, as well as a warehouse where spare parts are stocked.
Only certain repair shops are permitted to repair aircraft. Repair shops must comply with stringent training and certification standards to ensure that proper procedures are followed. Since aircraft are mobile, they can be flown to a repair shop with appropriate repair capacity and capabilities when routine maintenance becomes necessary. However, if a critical component fails, the aircraft may need to be grounded and repaired in place. Some repairable aircraft components are very large and/or require involved repair procedures by skilled repair technicians. For example, some repair shops will not have sufficient staff and/or space to repair more than one large fuselage piece or other large aircraft structure at a time. Hangar and associated workspace may be limited, and machines and equipment necessary to repair such components may be expensive so that a given repair shop may have only one set of equipment to work on a single component at a time. Such components might include for example flight control surfaces and sidewall panels; large structures including sheet metal and floorboards; interior components such a galleys, lavatories, cargo nets, seats, and class dividers; and accessories such as pumps, propellers, and toilet tanks.
Mathematical models for optimizing the performance of repairable components based on maintenance interventions have been widely discussed in the literature. An overview of maintenance models for repairable items is presented in Dekker, R., Applications of Maintenance Optimization Models: A Review and Analysis, Reliability Engineering and Systems Safety, Volume 51 (1996), incorporated by reference. Planning maintenance interventions can be a complex task because there are many variables involved. Gathering and combining all this information in order to generate an optimized maintenance plan is a challenge faced by maintenance planners.